NON-AQUEOUS LIQUID CLEANING COMPOSITION

Abstract: Non-aqueous liquid cleaning composition comprising a non-aqueous organic solvent, solid particles dispersed in the solvent and hydrophobically modified amorphous silica particles wherein a part of the hydroxyl groups on the surface of said silica particles has been silylated with a chlorine-free silylating agent.

Description: NON-AQUEOUS _.IQUID Cl-EA I g COMPOSITION Field of the Invention The present invention relates to non-aqueous liquid cleaning composition containing particulate solid material. Background of the Invention Non-aqueous liquid compositions, essentially constituted by a suspension of solid particles dispersed in a non-aqueous organic solvent, have already been disclosed in EP-A-490,436 (Unilever) or WO-A-91/12312 (Unilever) . Sedimentation of the solid components leads to the formation of an essentially solid-free transparent upper liquid layer (so called clear layer separation) which is not acceptable. To minimize the formation of a clear layer some sort of stabilising system is necessary. Such a system must reduce sedimentation without causing excessive viscosity increase. WO-91/12312 discloses that the physical stability of non- aqueous liquid cleaning compositions can be improved if hydrophobically modified amorphous silicas are added, the number of hydroxy- groups at the surface of the silica particles being reduced by substituting the free hydroxy- groups at the outer surface of the silica particles by less hydrophilic groups such as short alkyl groups. In this document, a precipitated silica, Sipernat D17 (obtainable from Degussa) , is used as a dispersant. Sipernat D17 is a precipitated silica having a BET surface area of 110 m/g and Cl ~ content of 0.05 % by weight. M.A.S.- N.M.R. analysis proves that hydrogen atoms of hydroxy groups at the surface of silica particles have been substituted by a dimethylsilylating agent (the silane peak being at around -18 ppm for a reference of 0 ppm for Tetramethylsilane) . It is believed that Sipernat D17 is produced according to US-A-4,208,316 (Degussa) . In this document is described a process for the production of hydrophobic precipitated silicic acid which comprises providing an aqueous alkaline suspension containing a hydrophilic silicic acid and introducing into the above a hydrophobic producing agent while maintaining an alkaline pH value. In Example 2, dimethyldichlorosilane ( (CH 3 ) 2 SiCl 2 ) is used as the hydrophobic producing agent. Even though a good stabilization of the cleaning composition is obtained, some problems still occur such as: the viscosity of the cleaning composition is increased by the addition of the silica, gas is formed in the cleaning composition during storage leading to the formation of craters at the surface of the cleaning composition. It has now been found that by using a specific class of hydrophobically modified amorphous silica particles it is possible to keep the viscosity of the system within satisfactory limits while reducing the formation of craters at the surface of the cleaning composition. It has also been found that the formation of a clear layer at the upper surface of the dispersion was also significantly decreased. General Description of the Invention It is a first object of the present invention to provide a non-aqueous liquid cleaning composition comprising a non- aqueous organic solvent, solid particles dispersed in the solvent and hydrophobically modified amorphous silica particles wherein hydroxyl groups on the surface of said silica particles have been silylated with a chlorine-free silylating agent. The non-aqueous liquid composition can be as described in WO-91/12312 or in EP-490436, included in the description by reference. The amorphous silica particles are preferably amorphous precipitated silica particles. Tests and Standard Procedures i) Viscosity The viscosity was measured using a Haake CV20 viscometer, a ZA30 'cup & bob' arrangement being employed. The viscosity was measured at 25°C. A shear rate of 21 s-1 was applied for 5 minutes and the viscosity determined at the end of this 5-minute period at the constant shear rate. ii) Clear Laver Separation (CLS) 1. Measure 100mm on side of a 500 ml PVC bottle(dimensions 232mm high x 57mm diameter) with a permanent marker pen. 2. Fill bottle, up to 100 mm, with the cleaning composition to be tested and seal it to keep out atmospheric water. 3. Place the bottle upright on a flat surface at 37°C. 4. The Clear Layer Separation (CLS) is assessed whilst the bottle is on flat surface using a ruler scaled to 0.5mm increments. iii) Hydrophobe Level (Methanol Number) 50 cm3 of demineralised water was placed in a 250 cm3 glass beaker. 0.20g of the silica to be tested was added to the water. Methanol was then titrated onto the silica. The end point is the point at which all the silica had descended to the bottom of the beaker. The methanol number is calculated from the formula: Methanol number = ml of methanol x 100 50+ ml of methanol iv) Gas Formation 15Og of the non aqueous liquid cleaning composition of the invention is put in a 200ml glass bottle supplied with a rubber stopper. Measurement of the pressure is carried out with a manometer (Digitron P200 AH) supplied with a syringe needle that can be stuck through the rubber stopper. The samples are stored at 37°C. It has been established that this method is very accurate and reproducible with no loss of gas. Specific Description of the Invention The invention will be further described in the following example. Preparation of Hvdophobicallv Modified Silica Amorphous silica (Neosyl TS obtainable from Joseph Crosfield __ Sons - Warrington - U.K.) is added into a 900 litre Nautamixer using a Wilden pump. During the addition, silica is agitated with a mixer. The required weight of silylating agent is added to the stirred silica over a period of 10 minutes by nitrogen pressure transfer (0.5 bar). Agitation is continued through¬ out addition and subsequent reaction period of 2 hours. Two different silylating agent were used, Hexamethyl- disilazane (HMDS) and Dimethyldichlorosilane (DMCS) . Example 1 The following cleaning composition (in parts by weight), as disclosed in Table I, was prepared by mixing the ingredients and milling to a mean particle size of 5μm. Table i Composition Parts by weight Nonionic (C10-12 alcohol ethoxylated 49.7 with an average of 6.5 EO groups) Alkyl benzene sulphonic acid 6 Sodium carbonate 17 Calcium carbonate 6 Sodium carboxymethyl cellulose 1.5 Sodium perborate monohydrate 10.5 Hydrophobically modified silica 4.5 Minors 4.8 The tendency of the composition to form a clear layer was determined according the above described method. The methanol number was also assessed. The viscosity was also measured initially (i.e. just after the preparation of the formulation) and after 4 weeks and 8 weeks according to the above described method. Six samples were tested wherein the silica had been hydrophobically modified as hereabove described using 5%, 6%, 7%, 8%, 9% and 10%of HMDS, (percentage by weight of HMDS added per weight of silica) . A first comparative sample, wherein Sipernat D17 was used as hydrophobically modified silica, was also tested. A second comparative sample, wherein the silica had been hydrophobically modified as hereabove described using 10% of DMCS (percentage by weight of DMCS added per weight of silica) , was also tested. Gas formation was assessed after 8 weeks and 12 weeks. The gas formation was assessed by estimating the number of craters formed at the surface of the cleaning composition using the following scale: 0 - Nil 1 - Slight 2 - Moderate 3 - Considerable The results are summarized in the following Table II. Table U Gas 5% 6% 8% 9% 10% 10% D17 formation HMDS HMDS HMDS HMDS HMDS DMCS after 8 weeks 0 0 0 0 0 1/2 2 12 weeks 0 0 1 1 1 2 3 The gas formation assessed, as here-above described was more precisely measured using the pressure increase which can be observe during storage. The results are summarized in the following table III wherein the pressures are in mPa. Table in Pressure 5% 6% 8% 9% 10% D17 HMDS HMDS HMDS HMDS HMDS Initial 1017 1003 1018 1008 1010 1010 after 1015 1014 1003 997 998 1074 8 weeks It is clear that, by using an amorphous silica hydrophobically modified by a chlorine-free sylilating agent, gas formation is dramatically reduced. The results of the viscosity and clear layer (CLS in mm) measurements are summarized in the following Table IV wherein the viscosity is in Pa.s. It is immediately obvious that, with the noticeable exception of the sample using 5% HMDS, the viscosity of the system, for an hydrophobici y at least equivalent to the hydrophobicity obtained when using Sipernat D17, is maintained well below 1200 mPa.s which is supposed to be the limit for a good pourability. The high viscosity observed when using 5% HMDS is explained by the fact that it has been found that regions of hydrophilicity cause increases in viscosity due to H-bonding network formation through surface silanols.

Claims: CLAIMS 1. Non-aqueous liquid cleaning composition comprising a non-aqueous organic solvent, solid particles dispersed in the solvent and hydrophobically modified amorphous silica particles wherein hydroxyl groups on the surface of said silica particles have been silylated with a chlorine-free silylating agent. 2. Non-aqueous liquid cleaning composition according to claim 1 wherein the chlorine-free silylating agent is hexamethyldisilazane. 3. Non-aqueous liquid cleaning composition according to claim 2 wherein the amorphous silica particles are amorphous precipitated silica particles.

Inventors: CARTWRIGHT SIMON, MINIHAN ALAN REGINALD, VAN DER HOEVEN PHILIPPUS CORNE, CARTWRIGHT, SIMON, MINIHAN, ALAN, REGINALD, VAN DER HOEVEN, PHILIPPUS, CORNELIS
Applicants: CARTWRIGHT SIMON, CROSFIELD JOSEPH & SONS, HOEVEN PHILIPPUS CORNELIS V D, MINIHAN ALAN REGINALD, CARTWRIGHT, SIMON, JOSEPH CROSFIELD & SONS LIMITED, MINIHAN, ALAN, REGINALD, VAN DER HOEVEN, PHILIPPUS, CORNELIS
Application year: 1994
Main classification: C11D17
IPC codes: C11D3, C11D17